Generally, batteries may be subjected to cycles of discharging by which chemical energy is changed into electrical energy, and charging by which electrical energy is changed into chemical energy. Most common batteries may be a lead-acid batteries, an application of galvanic cells. A lead-acid battery may consist of a Pb electrode and a PbO2 electrode in a concentrated sulfuric acid solution, and a lifetime of the lead-acid battery may be reduced due to various forms of aging processes including a change in an internal active material after the cycles of charging and discharging for a long time and a self-discharging phenomenon.
Meanwhile, the above-described battery may be periodically charged through a charger. Normally, such the charger may serve to charge a battery, but may not serve to diagnose a status of battery. Accordingly, since users do not know a lifetime of a battery while using the battery, the users may not recognize an inoperative state or failure sign of a system, caused by a sudden ending of a battery lifetime, in advance. Accordingly, a reliability of a system using the battery may be lowered.